The U.S. Navy said in a statement that no one was hurt when the U.S. Navy guided-missile destroyer and a large Japanese owned merchant vessel, M/V Otowasan, collided near the crowded Strait of Hormuz on August 12.

The collision happened 1 a.m. local time and left a breach about 10 feet by 10 feet in the starboard side of the USS Porter.

According to U.S. Navy officials, an investigation is underway to find out the cause of the incident. The USS Porter on a scheduled deployment to the U.S. 5th Fleet, which is based in Bahrain, an island nation in the Gulf, near Iran.

Greg Raelson, Navy spokesman, said the destroyer is now in port in Jebel Ali, Dubai. “We’re just happy there were no injuries,” he said. “An investigation is under way.”

The Strait of Hormuz is situated at the mouth of the Gulf. It is a crowded and tense waterway, with shipping lanes of about two miles wide in each lane.  Tensions have intensified over Iranian threats to block the straight, where one-fifth of the world’s oil is routed, to international shipping in retaliation for tighter sanctions by the West. The sanctions are aimed at persuading Iran to abandon its uranium enrichment program, so far without success.